Project Summary/Abstract Millions of American experience acute and chronic pain. Despite considerable progress identifying pathophysiologic mechanisms of acute and chronic pain, available treatments remain inadequate. Consequently, there is a compelling public health need for the development of treatments with improved efficacy, safety, and tolerability. Unfortunately, numerous analgesic treatments examined in recent randomized clinical trials have failed to show efficacy. The explanations for these negative results are unknown, raising questions about the ability of clinical trials in chronic pain to distinguish efficacious treatments from placebo or less efficacious treatments (i.e., assay sensitivity). Patient characteristics, clinical trial research designs and methods, outcome measures, approaches to data analysis, and statistical power may all play a role in accounting for difficulties in demonstrating the benefits of efficacious analgesic treatments vs. placebo. The identification of specific clinical trial characteristics associated with assay sensitivity in existing data has the potential to establish an evidence-based approach to the design of analgesic clinical trials. The U.S. Food and Drug Administration recently launched Analgesic Clinical Trial Innovations, Opportunities, and Networks (ACTION), a public-private partnership intended to facilitate the discovery and development of analgesics with improved efficacy, safety, and tolerability for acute and chronic pain. ACTION will establish a collaborative initiative to prioritize research objectives, develop a standardized analgesic database platform, and conduct methodologically-focused studies to increase the assay sensitivity and efficiency of analgesic clinical trials. The results of these studies and other activities have the potential to inform and accelerate the development of improved pain management interventions of all types, not just pharmacologic treatments.